ACTIVITY OF LIPOXYGENASE ISOENZYMES DURING MALTING AND MASHING

The objective of this study was to evaluate the development and stabil ity of the lipoxygenase (LOX) isoenzymes LOX-1 and LOX-2 during maltin g and mashing. LOX-2 was detected only in grminating barley, while LOX -1 was present in sound grain. The activity of both isoenzymes increas ed during germination. Total LOX activity, and the ratio of LOX-1 to L OX-2, varied among the three samples used in this study. LOX-1 and LOX -2 activities decreased at similar rates during kilning, and only 1-3% of the total LOX developed remained in the micromalts. The remaining activity was primarily LOX-1. The two commercial malts tested containe d higher LOX activities. During mashing, about one third of the total LOX was extracted into the wort. The majority of the activity remained in the grist and was more thermostable than that in the wort. LOX act ivity was also affected by germination temperature. The addition of gi bberellic acid (GA(3)) and abscisic acid (ABA) was determined to have no significant effect on LOX activity.